It happens, doesn't it, when someone is killed. Whether that person was a war reporter or journalist or somehow a public figure, the reaction is the same: their work was astonishing. He or she was an incredible person with hundreds of friends. There is a hagiographic pattern to the public mourning that doesn't always convince because it happens as rote. But with all the praise given to Chris Hondros since he was killed by a mortar attack in Libya just over three years ago – it's all true. He really was that good. He really was that loved.

I first encountered Chris online. I was writing a book on Liberia, and I found an essay he'd written (reproduced in Testament) about a shell attack in Monrovia. It was thoughtful, observant. I was intrigued. A photographer who could actually write? There aren't many of those. I emailed him asking if I could quote his essay; he emailed back; we became friends. I always knew that, out of the two of us, he was the proper journalist. I have avoided war; he was always in it. I would see him in London sometimes, when he was returning from a month or so embedded in Iraq or Afghanistan.

From the outside, Hondros fitted the profile of a war photographer, with his cameras slung around his neck, his fisherman's vest and combat trousers, his boots for the desert. He was charming, debonair. But his ability went wider and deeper than that stereotype. In New York, after several trips to Iraq, he began to put on sound and vision concerts, where his images would play alongside Bach, to raise money for Iraqi causes. In Iraq, on one of his many embeds with the US military, he lay outside in the Anbar desert and looked in his head for the music "that best conveys the tragedy of Iraq". Bach again? Mahler? But "this war is too ambiguous for Mahler". He settled on the late string quartets of Beethoven: "the long, ambiguous, introspective elegies so characteristic of these late quartets – like the lento assaimovement of the F major or the lovely cavatina of the B flat – oddly, in their stillness and intimacy, might come as close as we can get to comprehending the madness of war."

A good war photographer will photograph war and battles, but the best comprehend that war is fought around and through civilians, who make up the majority of war casualties these days. So in the images in this book there are the exhausted US soldiers and terrifyingly young boy soldiers of Liberia's wars, blank aggression on their faces. But there is stillness too, in the deep green stagnant pond in an abandoned Iraqi palace, or in a young Liberian woman in a dead faint at a political rally, borne on the shoulders of the crowd, her position one of ecstasy or crucifixion. Hondros wanted to take portraits of people but also countries: full portraits that incorporated the aftermath of war as well as its appalling presence.

An unconscious woman is carried over the heads of the crowd at a political rally in Liberia. Photograph: Chris Hondros/Getty Images

My favourite Hondros picture is here, of a young fighter on the bridge separating Bushrod Island with central Monrovia in Liberia. Hondros had to walk across a bridge in a raging battle to take the picture, and he undertook the walk not just to take the shot, but to ask a question of the Liberians United for Reconciliation and Democracy (Lurd) rebels on the other side: what were they fighting for? But they didn't really know, as the government fighters Hondros had just left didn't know either. That bridge walk is a story still told among Chris's friends. They recount their stories of Chris to keep him alive, writes Greg Campbell. One remembers Chris "talking about how terrified he was and about how he thought about turning back many times … But then he said, 'You know, I didn't cover all that high school football just to come this far and turn back.'"

That is deceptive flippancy, because once that Liberia picture had become globally famous, Hondros went back to the country when the war was over in 2003. He found the young man and paid for his schooling.

In 2005 he was with an evening US foot patrol in Tal Afar – a "rough town", he wrote in an article for the Fort Collins Weekly – in northwestern Iraq. A car approached the patrol and didn't stop. There were warning shots then a cacophony of gunfire. "Then came the sound of crying children from the car. A teenage girl with her head covered soon emerged from the back seat, wailing and gesturing wildly. After her followed an injured boy, who left behind a pool of blood in his seat. More children – six in all – emerged, crying, their faces mottled with blood in long streaks. 'Civilians!' someone shouted."

Civilian children. Five-year-old Samar Hassan, shown screaming in one of Hondros's most famous images, after her parents had been shot dead; 12-year-old Rafan, her brother, shot in the back, eventually sent to the US for treatment after Hondros's pictures caused a major scandal, then returned to Iraq where he was killed at the age of 16 in a bomb that landed on his house.

The Tal Afar pictures had an immediate impact. They portrayed the US role in Iraq unmistakably. They were hard to look away from. The series won the Robert Capa Gold Medal and many other awards, and got Hondros an invitation to lunch with Paul Wolfowitz, second-in-command at the Pentagon at the time. Wolfowitz was fascinated by a man who had experienced the war he was waging remotely. Even the soldiers on the ground, Hondros wrote in one blog post for his employer Getty Images, saw Iraq only by peering through the windows of a Humvee. He called this Humvee TV, because "the window of a Humvee rolling through Baghdad's dangerous streets is essentially a television, watched in the dark. The glass is dirty and three inches thick, and everything has a hazy, muted look. Humvees are dim inside, even on sunny days. You can see out, but Iraqis can't see in, any more than sitcom characters can see you watching."

We watch war through TV too. It is people like Hondros who make the victims of the terrible conflicts in Iraq, Liberia, Afghanistan, Syria, Libya emerge from their role on our TV news. He makes them real, as they should be.

In Sebastian Junger's documentary about Tim Hetherington, who died in the same mortar attack as Chris, there is an early scene in a car in Libya. It is 20 April 2011, a few hours before the mortar attack. The camera moves from the driver to the passenger seat behind. And there is Chris, looking peaceful, looking alert, a glint in his eye, watching the world for us. He is missed.

• To order Testament for £22.50 with free UK p&p call Guardian book service on 0330 333 6846 or go to guardianbookshop.co.uk.